Aortic Scaffold Fabrication with Allevi

This thesis work by Benjamin Stewart from the University of Denver uses an Allevi Beta printer to fabricate analyze scaffolds for thoracic aortic grafts.

An allevi platform is used in this work for the fabrication of aortic scaffolds.

Abstract: The gold standard in 2016 for thoracic aortic grafts is Dacron®, polyethylene terephthalate, due to the durability over time, the low immune response elicited and the propensity for endothelialization of the graft lumen over time. These synthetic grafts provide reliable materials that show remarkable long term patency. Despite the acceptable performance of Dacron® grafts, it is noted that autographs still outperform other types of vascular grafts when available due to recognition of the host’s cells and adaptive mechanical properties of a living graft. 3-D bioprinting patient-specific scaffolds for tissue engineering (TE) brings the benefits of non-degrading synthetic grafts and autologous grafts together by constructing a synthetic scaffold that supports cell infiltration, adhesion, and development in order to promote the cells to build the native extracellular matrix in response to biochemical and physical cues. Using the BioBot’s 3-D bioprinter, scaffold materials we tested non-Newtonian photosensitive hydrogel that formed a crosslinked matrix under 365 nm UV light with appropriate water content and mechanical properties for cell infiltration and adhesion to the bioprinted scaffold. Viscometry data on the PEGDA-HPMC 15%-2% w/v hydrogel (non-Newtonian behavior) informed CFD simulation of the extrusion system in order to exact the pressure-flow rate relationship for every hydrogel and geometry combination. Surface tension data and mechanical properties were obtained from material testing and provide content to further characterize each hydrogel and resulting crosslinked scaffold. The goal of this work was to create a basis to build a database of hydrogels with corresponding print settings and resulting mechanical properties.